"""Helpers to mutate a quadrant fixture at grid coordinates."""


def grid_lines(text: str) -> list[str]:
    """Grid lines without comments, right-padded to full width, as the parser sees them."""
    lines = [line for line in text.splitlines() if line.strip() and not line.startswith("#")]
    width = len(lines[0])
    return [line.ljust(width) for line in lines]


def edit(text: str, line: int, column: int, replacement: str) -> str:
    """Overwrite characters of grid line ``line`` (0-based, comments excluded) at ``column``."""
    lines = grid_lines(text)
    target = lines[line]
    lines[line] = target[:column] + replacement + target[column + len(replacement) :]
    return "\n".join(lines) + "\n"


def cell_line(row: int) -> int:
    return 2 * row + 1


def wall_line_above(row: int) -> int:
    return 2 * row


def cell_column(col: int) -> int:
    return 4 * col + 2


def wall_column_left_of(col: int) -> int:
    return 4 * col


def h_segment_column(col: int) -> int:
    return 4 * col + 1